High-throughput molecular biologic and proteomic methods provide several promising approaches for relating genetic changes, such as mutation or altered gene expression, to metastasis, to treatment outcomes, and to survival. In cancers where the interval between initial diagnosis and treatment and the appearance of metastases is long, clinical correlations would be more readily obtained if formalin-fixed paraffin-embedded (FFPE) tissues could be used instead of fresh or frozen specimens. Large-scale multiplex techniques, such as serial analysis of gene expression (SAGE), and gene chip methods yield experimental results that are somewhat different for FFPE tissue and unfixed tissue. The long-term goal of our research program is to use high-throughput molecular biologic screening methods to identify the molecular and genetic basis of cancer origins and behavior. The objective of this proposal is to identify the formaldehyde-induced chemical modifications that occur to nucleic acids during histologic tissue processing and to develop methods to reverse these modifications. Our centralhypothesis is that formaldehyde adducts and cross-links formed during tissue processing can be sequentially reversed by a series of heating and dialysis steps, carried out under appropriate solvation conditions. We formulated this hypothesis on the basis of preliminary data which show that the reversal of formaldehyde-induced chemical changes in proteins and nucleic acids is relatively facile in aqueous solutions, but less so following dehydration in the presence of organic solvents. The rationale for these studies is that their successful completion will provide a foundation for applying high-throughput screening methods to FFPE tissues. This will lead to improved practical interventions for the diagnosis, evaluation, treatment, and prevention of cancer and facilitate the development of therapeutic agents. Our studies are innovative in that we have pioneered a novel model system (tissue surrogates) ideally suited to identify the formaldehyde-induced modifications to proteins and nucleic acids that occur during tissue processing. At the completion of this project it is our expectation to have established a comprehensive understanding of the formaldehyde-induced chemical modifications to mRNA that occur during tissue histology, and methods for optimally reversing these modifications. This knowledge should result in an ability to carry out genomic analysis on FFPE tissue, significantly expanding our capability to conduct genomic research and opening important new areas to practical investigation.